1. Field of the Invention
This invention relates to an apparatus for processing and handling slag formed in smelting furnaces and units and more especially to an apparatus for granulating molten slag.
This invention may find a most effective application both for processing partly solidified slags transported in ladles out of smelting shops and for processing slags directly by blast furnaces and steelmaking units (e.g. converters).
2. Description of the Prior Art
At present, a wide use is made of installations for granulating slag comprising a water pool, a water-jet apparatus with a launder and an open-air area for the storage of granulated slag (see, for example, USSR inventor's certificate no. 138,518, Int. Cl.CO4b5/02, 1959). Such installations are located at a great distances (up to 1.5 km and more) from smelting plants, and molten slag is transported thereto in ladles carried by locomotives.
Water for granulating molten slag is injected into the launder of the installation, and, at the same time, molten slag is poured thereinto from slag ladles. A resultant slagwater pulp is sprayed upon in an open-air storage area, and after excess water drains off, the slag is piled, and then loaded by grab bucket devices into railway cars for transportation to consumers (e.g. cement works). Drained water flows by gravity into settling basins composed of several sections to ensure more effective clarification.
The disadvantages of slag granulation in such installations are as follows:
high moisture content of granulated slag;
complicated system of recycled water supply (including extensive piping, pumps, fittings, settling basins, etc.), which, due to the tendency of the fine slag particles to cement, requires considerable and other means for frequent repairs required to maintain such system;
risk of explosions when molten iron flows together with slag and/or slag skulls fall into the launder;
need for large open-air storage areas for granulated slag and a water recycling system with settling ponds.
There is known in the prior art an installation for granulating and dewatering slag, located beside a blast furnace (see USSR inventor's certificate no. 529,132, Int. Cl. CO4b5/02, 1971), comprising a closed water-jet granulator with a launder and a pulp-receiving bin with an overflow device located at the launder's outlet. The bin is connected by means of an airlift with a device for dewatering slag, and a receptacle for filtered water with a discharge pipe is provided underneath said device. Underneath the pulp-receiving bin, there is also a clarified water tank communicating in its bottom part with a pump for supplying said clarified water to the water-jet granulator. The pulp-receiving bin is provided with a screen for separating large foreign inclusions and slag skulls.
Molten slag from the blast furnace flows into the launder where it is granulated by jets of water supplied under pressure by pumps from the clarified water tank.
Pulp resulting from granulation enters a pulp-receiving bin where granulated slag settles, whereas clarified water passes over an overflow device into the clarified water tank and is recycled by a pump to the water-jet granulator. Slag settling in the bottom part of the pulp-receiving bin forms with water a thick pulp which is conveyed by an airlift to a dewatering device where filtered water returns via a pipe to a pulp-receiving bin, and whereas dewatered granulated slag is transported by a conveyor to storage or to railway cars. A water vapour-gas mixture formed in the process of granulation is exhausted to the atmosphere.
The disadvantages of slag granulation on such installations are as follows:
necessity for a protective screen in the pulp-receiving bin to prevent the plugging of the airlift by coarse foreign inclusions and slag skulls. These screens tend to be plugged gradually by large slag skulls, by lumps of refractory mass employed to line blast furnace runners and by other objects, with the granulated slag depositing thereon, all contributing to making difficult the servicing of the installation and reducing the time between maintenances and repairs;
relatively large requirements in area make difficult the introduction of said installations in the confined space of existing blast furnace plants. These installations are, as a general rule, built in new blast furnace plants located on new sites where there is usually much more room available.
A prior method closest in technological aspect to the present invention is that disclosed in U.S. Pat. No. 3,615,329, put into effect on an installation comprising a launder for supplying molten slag, a device for granulating and cooling granulated slag formed with a water-jet granulator, complete with launder and pumps, and a coarse slag particle-settling bin (section) which accommodates a vertical elevator with perforated buckets. The bottom part of the elevator is located inside the bottom part of the settling bin. For additionally cooling and cleaning water of fine slag particles, the installation is provided with cyclones and a water cooling system consisting of a cooling tower, a cooling tower basin, pumps and water supply fittings.
Molten slag is supplied along a launder (for example, from a blast furnace) into a water-jet granulator, where the slag is granulated by jets of cold water delivered under pressure by pumps. Pulp then enters the open settling bin where settled granulated slag is transported by the elevator to a handling conveyor. Slag is partly dewatered as it is being transported by the elevator. Hot water clarified in the settling bin and containing fine slag particles in suspension is injected tangentially into hydrocyclones where slag is separated from the water, and then hot water free from fine slag is cooled in cooling towers and recycled to the water-jet granulator.
The disadvantages of slag granulation on such installations are as follows:
a very complicated recirculatory water supply system (several groups of pumps, numerous fittings, settling basins, cooling towers with basins, cyclones);
risk of explosions when molten iron flows together with slag and/or slag skulls fall into the launders;
lack of devices for cleaning slag-formed vapors of sulfurous components;
poor dewatering of granulated slag when the water level in the elevator buckets is higher than that of the slag, this being due to fine particles in suspension in the water settling on the coarser slag and impairing water drainage.